The way emergency contraceptive
pills work depends on where you are in your monthly cycle when
you take them. EC works primarily, or perhaps exclusively, by delaying or inhibiting ovulation (release of your
egg). It is possible that EC may affect the movement of egg or sperm (making them less likely
to meet), interfere with the fertilization process, or prevent implantation
of a fertilized egg. The copper in Copper-T
IUDs can prevent sperm from fertilizing an egg and may also prevent
implantation of a fertilized egg.

For more discussion about how emergency contraception prevents pregnancy,
click here. You
can also read more about the difference between EC and medical abortion on this fact sheet from the American Society for Emergency Contraception.

Read a thorough and up-to-date academic review of the medical
and social science literature, including research into how emergency
contraception works, by clicking
here.